Supravital electrical excitability of muscles

A new method of postmortem electrical stimulation of muscles, measuring the force of the reaction against time, is presented. Preliminary investigations have yielded the following results: The maximum force of reaction in response to a definitive stimulation, measured by a sensitive force transducer, decreases in proportion to the post mortem interval. Using this method, the mechanical reactions of muscles by electrical stimulation can be demonstrated over a much longer postmortem period as these movements are visible. The duration of postmortem reaction of different muscles seems to be much more uniform than was previously assumed. Occasionally, reactions of the M. orbicularis oculi can be seen for the longest time. The basal muscular tonus changes relative to time. The time course of a single force reaction also changes relative to the postmortal interval: the reaction becomes slower. It has been theoretically established that measurement of influencing factors such as temperature and pH in the tested muscle will enable the time of death to be more precisely estimated.     

Estimation of the time since death

The main principle of the determination of the time since death is the calculation of a measurable date along a time-dependent curve back to the start point. Characteristics of the curve (e.g. the slope) and the start point are influenced by internal and external, antemortem and postmortem conditions. These influencing factors have to be taken into consideration quantitatively in order to improve the precision of death time estimation. It does not make any sense to study the postmortem time course of any analyte without considering influencing factors and giving statistical parameters of the variability. Comparison of different methods requires an investigation of the same postmortem interval. For practical purposes, it must be concluded that the amount of literature on estimating the time since death has a reverse correlation with its importance in practice.     

Postmortem interval estimation by biochemical determination in birds muscle

Experimental postmortem interval estimation was assayed by various biochemical components of hens pectoral muscle. Among them, only percentage of non-protein nitrogen on total soluble protein, asparatic amino transferase activity and creatinine concentration showed significant correlation with time after death. Asparatic amino transferase was negatively correlated and non-protein nitrogen percentage and creatinine were positively correlated to postmortem interval. The stronger correlation (0.925) was found for creatinine.     

不同环境条件下大鼠死后皮肤大体和组织学改变

目的研究观察大鼠在不同环境条件下死后不同时间其皮肤大体、组织学的改变,为推测较长的死后间隔时间建立实验动物依据。方法观察雌性SD大鼠在不同环境条件下的死后变化,并间隔一定死后时间取皮、染色和镜下观察。结果死后发生骨、软组织分离,A组约需35d,B组需13d。皮肤有形细胞成分和附属器完全分解破坏,A组约20d,B组7d。胶原纤维在A组死后40d（B组12d）仍有部分保留完整。结论环境温度差异是造成A、B两组发生死后改变时程不同的主要因素,利用皮肤大体、组织学改变可望较系统和准确的推测晚期死亡时间。     

Nocturnal Oviposition Behavior of Forensically Important Diptera in Central England

Timing of oviposition on a corpse is a key factor in entomologically based minimum postmortem interval (mPMI) calculations. However, there is considerable variation in nocturnal oviposition behavior of blow flies reported in the research literature. This study investigated nocturnal oviposition in central England for the first time, over 25 trials from 2011 to 2013. Liver-baited traps were placed in an urban location during control (diurnal), and nocturnal periods and environmental conditions were recorded during each 5-h trial. No nocturnal activity or oviposition was observed during the course of the study indicating that nocturnal oviposition is highly unlikely in central England.     

Postmortem production of ethanol in different tissues under controlled experimental conditions

The aim of this study was to follow the postmortem ethanol production phenomenon under controlled experimental conditions (temperature, time interval) in different tissues. Specimens of blood, liver, skeletal muscle and kidney were taken from 30 corpses and no chemical preservatives were used in the specimens collected. Ethanol concentrations were detected by gas chromatography. All specimens stored at -20 degrees C and 4 degrees C did not show any change in ethanol concentration in an eight-day time interval. At 20 degrees C and 30 degrees C, all tissues, except blood, showed statistically significant ethanol production over the time interval tested. However, blood sample kept at 30 degrees C, showed statistically significant increase in ethanol production on the 2nd and 4th day comparing to the controls. Thus, we can state that postmortem ethanol production occurs in different tissues, and is increased at higher temperatures and, in general, it is in accordance with the course of time.     

Postmortem DNA and RNA synthesis. Preliminary studies in human cadavers

Postmortem DNA and RNA synthesis was detected in tissue specimens harvested from two cadavers at different intervals between 2.5 and 32 h postmortem. Each tissue specimen was incubated for 1 h in a 3H-thymidine or 3H-cytidine solution. DNA- as well as RNA-synthesizing cells were found in skin tissue and bone marrow throughout the interval investigated. Cytidine incorporation decreased progressively during the course of the postmortem interval. DNA and RNA synthesis was also observed in cells of the testis, which were predominantly spermatogonia cells in the case of DNA. Low-grade RNA synthesis was detected in bowel epithelial cells up to 2.5 h postmortem; DNA synthesis was not present during the interval investigated. No supravital phenomena were observable in the splenic tissues examined.     

The use of absolute refractory period in the estimation of early postmortem interval

The estimation of the time since death (postmortem interval) is one of the most difficult problems in forensic pathology. Most methods currently employed use temperature-based algorithms intended to model the cooling of the body after death and thus estimate the postmortem interval. These methods are subject to considerable inaccuracy but their reliability can be improved if a range of other observed criteria such as lividity and rigor are also taken into consideration. The aim of the present study was to investigate the feasibility of using the absolute refractory period as an adjunct to the estimation of postmortem interval. The relationship between the `postmortem interval' and the `duration of absolute refractory period' was investigated using the rat sciatic nerve. A strong correlation between the duration of the absolute refractory period and the postmortem interval was observed. When both absolute refractory period and temperature were used in conjunction, the strength of this correlation was increased.     

Estimation of postmortem interval using the protein marker cardiac Troponin I

The importance of determining the time since death is crucial to criminal, civil and forensic cases. A technique exploiting the degradation of a protein, cardiac Troponin I (cTnI), to estimate the postmortem interval (PMI) was investigated. Cardiac Troponin I is a basic regulatory protein found as part of a ternary complex responsible for calcium dependent muscle contraction. An efficient extraction protocol to analyze the banding pattern of cTnI in postmortem tissue was developed. The analysis involves extraction of the protein, separation by denaturing gel electrophoresis (SDS-PAGE) and visualization by Western blot using cTnI specific monoclonal antibodies. A bovine model was used to develop and optimize the protocol. The homology of cTnI amongst mammalian species allows for the cross-reaction of human anti-cTnI antibodies with bovine cTnI. The results indicate a characteristic banding pattern amongst human cadavers (n=6), a pseudo-linear relationship between percent cTnI degraded and the log of the time since death (r>0.95), and a qualitative degradation band pattern that in a simple comparative analysis with a standard human heart (known time since death) can be used to estimate the postmortem interval. The degradation-banding pattern of tissue cTnI is useful in the determination of the early postmortem (pm) interval (0-5 days). Overall, this technique offers advantages such a wide postmortem interval, measurable degradation pattern, a temporal semiquantitative relationship and manageable temperature dependence over direct temperature methods.     

Preliminary study of the effect of acute antemortem haemorrhage on postmortem abdominal impedance in rats

Studies over many years have revealed a consistent, inverse relationship between extracellular impedance of the rat abdomen and postmortem interval (PMI). Recent studies have shown that this relationship can be improved by correcting measured impedances to their theoretically predicted values at an arbitrarily chosen temperature of 40 degrees C, thus rendering them independent of the tissues' temperature at the time of impedance measurement. The present study, undertaken as a part of an ongoing effort to identify variables which might influence postmortem rate of change in abdominal impedance, was aimed at studying the possible effect of acute antemortem haemorrhage on abdominal impedance. Sudden loss of approximately 30% of the total blood volume, immediately prior to the death was without statistically significant effect on the pattern of postmortem change in abdominal impedance. Thus, in the control and experimental rats, respectively, impedance decreased progressively from 58.7 +/- 1.8 and 68.0 +/- 11.3 omega, 1 h postmortem, to 31.5 +/- 2.2 and 33.7 +/- 4.7 omega at a postmortem interval of 120 h (n = 6 in each group). In both groups, the relationship between impedance and postmortem interval was either linear or curvilinear. These findings are believed to mitigate in favour of continued effort to examine the potential usefulness of abdominal impedance, as an index of postmortem interval, under conditions encountered in routine forensic investigation.     

Amount of postmortem bleeding: an experimental autopsy study

An experimental autopsy study was performed on 64 cases (55 male, 9 female; average age 51.5 +/- 16.2 years) of sudden natural (38 cases) and asphyxic deaths (26 cases). The study objective was the amount of postmortem bleeding from postmortem cutting of the thoracic aorta, related to the time since death. The amount of postmortem bleeding ranged from 100 to 1300 cm, 440.6 +/- 268.1 cm on average. The time since death up to the autopsy time ranged from 4 to 72 hours, 19.4 +/- 12.9 in average. A statistically significant correlation between the amount of postmortem bleeding and postmortem time interval was stated: Pearson correlation test value r = -0.461 (P = 0.000): the shorter the time interval, the larger the amount of bleeding. The formula of linear regression was estimated according to this correlation: amount of postmortem bleeding (cm) = -9.571 x time since death (h) + 626.659. This proves that the amount of postmortem bleeding (eg, from aortic blunt rupture) could be about 620 cm.     

Vitreous humor biochemical constituents: evaluation of between-eye differences

The present study was conducted to investigate the differences in the vitreous humor biochemical concentrations for vitreous electrolytes and calcium in the same pair of eyes at identical postmortem interval (PMI). The vitreous humor samples were collected independently in both eyes from 48 autopsies (PMI range, 4.5-84.3 hours) with documented time of death. The samples were analyzed for potassium, sodium, chloride, and calcium using a Beckman Coulter LX20 Automated Analyzer based on ion-selective electrode methodology. There were no statistically significant between-eye differences at identical postmortem interval. A significantly high correlation was observed between paired potassium concentrations of both the eyes. A highly significant linear correlation was observed between the individual eye and mean potassium concentrations of both the eyes with postmortem interval. The observed differences were not significantly correlated with postmortem interval. The results demonstrated that the between-eye differences for vitreous electrolytes and calcium are insignificant. Therefore, the utility of vitreous biochemistry, particularly potassium in postmortem interval estimation and other forensic applications, cannot be questioned solely on the basis of these differences.     

Estimation of short-term postmortem interval utilizing core body temperature: a new algorithm

The use of temperature-based short-term postmortem interval (PMI) estimation methods can be useful to homicide investigators at the scene of a questionable death; however, a number of current PMI estimation techniques have high error rates such that they are of limited utility to law enforcement investigators and forensic professionals. These methods fail to control confounding errors present in individual data. An averages-based method of short term postmortem interval estimation was compared to eight other methods, and found to predict postmortem interval considerably more accurately, and for much longer periods of time.     

家兔急性胰腺炎死后不同时间眼玻璃体液淀粉酶变化

目的探讨急性胰腺炎死后不同时间眼玻璃体液淀粉酶变化。方法用1%牛胆酸钠诱导家兔急性胰腺炎动物模型建立,于死后不同时间和正常对照组,观察其淀粉酶变化。结果家兔急性胰腺炎死后72h眼玻璃体液淀粉酶含量(x)与死亡时间(y)存在相关关系,并导出其二项式回归方程为y=8.7420 0.7699x-0.0083x2(R2=92.62792,F=14.89734,P=0.001)。可作为推定早期损伤时间的参考指标。结论家兔急性胰腺炎死后不同时间眼玻璃体液淀粉酶改变为法医早期死亡时间推断提供了灵敏客观的实验依据。     

Postmortem biochemical examination of synovial fluid--a preliminary study

Vitreous humor chemistry is used for postmortem analysis since serum values of many components are thought to be reflected in vitreous humor and to be stable for a prolonged postmortem interval (pmi). A similar isolated compartment to vitreous humor is synovial fluid which up to now was hardly used for postmortem chemistry.The aim of the present examination was to compare the values of various analytes in both fluid compartments to get first hints for the reliability of the examination of synovial fluid. Therefore, in 74 cases of sudden death both fluids were taken and analysed for natrium, potassium, calcium, chloride, urea, creatinine, and glucose. The results show that the examination of synovial fluid as compared to vitreous humor is a reliable method to get hints on the premortal metabolic status since most analytes are stable postmortem. The range of all values is comparable in both fluids. The time course of glucose concentrations and, much more important, potassium concentrations is nearly similar. If no vitreous humor is available synovial fluid may be used with all precautions in diagnosis known from vitreous humor.     

Temperature-correction of abdominal impedance: improved relationship between impedance and postmortem interval

The relationship between extracellular abdominal impedance and postmortem interval (PMI) reflects the combined effects, on impedance, of postmortem cooling of the tissues and of autolysis per se. This study was performed in order to eliminate temperature change as a major factor contributing to the time course of postmortem change in abdominal impedance. Dissociation of thermal and autolytic influences was achieved by recording deep abdominal temperature at the time of impedance measurement, followed by correction of all measured impedances to their theoretically predicted values at an arbitrarily chosen temperature of 40 degrees C. Uncorrected abdominal impedance increased from 82+/-12 Ohmz, 1 h after death, to 108+/-21 Ohmz after 12 h. Impedance then decreased to 96+/-23, 89+/-22, 75+/-19, 66+/-21 and 59+/-19 Ohmz at postmortem intervals of 24, 36, 48, 60 and 72 h, respectively. In contrast, corrected abdominal impedance decreased progressively from 63+/-7 Ohmz, 1 h after death, to 61+/-9, 56+/-11, 51+/-10, 46+/-10, 39+/-11 and 35+/-10 Ohmz at postmortem intervals of 12, 24, 36, 48, 60 and 72 h, respectively. The improved relationship between (corrected) abdominal impedance and PMI is of potential value in estimating time since death.     

Determination of calcium and magnesium in postmortem human vitreous humor as a test to ascertain the cause and time of death

The concentrations of magnesium and total calcium human vitreous humors obtained postmortem was tested. In the groups of heart disease and asphyxia a correlation between the postmortem interval and calcium or magnesium concentrations was found. There was no correlation between postmortem interval and calcium respectively magnesium in the other causes of death. It seems possible that the analysis of vitreous humor may be useful in both diagnosis and determination of postmortem interval in the cases of heart death and asphyxia.     

Flow cytometric evaluation of postmortem pulp DNA degradation

During postmortem autolysis, cellular organelles and nuclear DNA break down into their constituent parts. DNA flow cytometric analysis was applied to study the denaturation of splenic cell DNA as a possible method for postmortem interval determination. DNA denaturation continued for 72 hours at a constant rate, with no intact DNA peaks thereafter. The value of using dental pulp tissue for flow cytometric determination of postmortem interval was investigated. The pulps of 57 routinely removed impacted third molars from patients 15 to 30 years of age were obtained. Pulp tissue was removed at 24, 48, 72, 96, 120, and 144 hours postextraction. Debris (degraded DNA) was defined as all signals left of the standardized mean 2n peak and expressed as a percentage of the total number of signals. In contrast to the splenic cell DNA, dental pulp tissue exhibited minimal DNA degradation by 144 hours postextraction, and no constant relation was found between time and DNA degradation during this time. In this study, pulp tissue was found to be unreliable to determine the early postmortem interval but might be of greater value in the later stages.     

Linearization of the relationship between postmortem plasma chloride concentration and postmortem interval in rats

A potentiometric titration procedure was employed for measurement of plasma chloride concentrations during the 0-96 h postmortem period in rats. The data revealed antemortem absolute values and postmortem rate of decrease in plasma chloride concentration (PCl) which were almost identical to those in dogs and in man. Expression of the data in the form of a double logarithmic plot of PCl versus postmortem interval (PMI) yielded a linear relationship of high correlation (r = -0.97; P less than 0.001). Attention is drawn to the possibility of utilizing postmortem rate of change in plasma chloride concentration as a means of estimating time elapsed since death.     

心肌梗死6项免疫组化指标的死后稳定性比较

目的　探讨用于早期心肌梗死死后诊断的维连接蛋白 (Fn)、纤维蛋白原 (Fg)、补体 (C5 )、肌红蛋白(Mb)、肌动蛋白 (HHF3 5 )、结蛋白 (Dm )等 6项免疫组化指标在死后不同时间的稳定性。方法　应用免疫组织化学法、图像分析和统计学处理系统 ,检测缺血心肌细胞内Mb、HHF3 5、Dm的缺失面积和Fn、Fg、C5的阳性反应面积 ,并对 6项免疫组化指标在死后不同时间的稳定性进行比较。结果　正常心肌组织 4℃放置 1～ 2d ,Dm、HHF3 5、Mb染色均匀 ,未见明显缺失 ;放置 3d以上 ,即可见Dm、HHF3 5、Mb明显缺失 ,且随放置时间延长 ,缺失面积逐步增大。缺血心肌组织随放置时间延长 ,Dm、HHF3 5、Mb的缺失面积逐步增大 ,Fg、C5、Fn阳性反应面积逐渐减少 ;放置 14d以上 ,Fg呈阴性反应 ;放置 2 1d以上 ,C5呈阴性反应 ;放置 2 8d ,Fn仍呈阳性反应。正常心肌组织放置不同时间 ,均未见Fg、C5、Fn阳性反应。图像分析结果显示阳性反应面积逐步减少。结论　Dm、HHF3 5、Mb的稳定性最差 ,易受死后自溶的影响 ,只适用于新鲜尸体 (死后 1～ 2d) ;Fg次之 ,可用于死后 4℃放置 7d的尸体 ;C5较好 ,可用于死后 4℃放置 14d的尸体 ;Fn稳定性最好 ,可用于死后 4℃放置 2 8d的尸体。